A possible mistake in the DVD commentary?

In the MPI Complete Sherlock Holmes DVD collection, Hound has a commentary by David Stuart Davis. In this commentary, Davis claims that Sir Hugo Baskerville (the loutish ancestor we see in the flashback) was "obviously" played by Richard Greene (the top billed actor playing the "modern day" Sir Henry Baskerville) wiht a fake beard.

The problem with this claim is that the role of Sir Hugo is credited to someone else, Ralph Forbes, and Ralph Forbes is no pseudonym. He was an actor with a fairly busy career in the 1930s. He even co-starred with Basil Rathbone in a couple of Basil's better known non-Holmes films: Romeo and Juliet where he played Paris to Basil's Tybalt, and, the same year Hound came out, Tower of London, playing Henry Tudor to Basil's Richard III (IOW, he's the dude that gets to kill Basil at the end). He even had an actress mother, Mary Forbes, who became part of the "Holmes stock players" appearing in no fewer than three of the Rathbone-Bruce Holmes films: The Adventures of Sherlock Holmes, Sherlock Holmes in Washington, and Terror by Night. Ralph Forbes is not only credited in the closing credits as playing Sir Hugo, he even gets billing in the opening credits.

If Davis is right about this, and Sir Hugo was actually played by Richard Greene in a dual performance, than he should've addressed the question of why Forbes is so prominently credited with the role if he didn't play it. He never does in the commentary. Which makes it more probable that Davis merely made an assumption that is actually dead wrong.